Off Road Suspension: Getting the perfect set-up
Off Road Suspension: Getting the perfect set-up
- Julian
- January 25, 2017
- 9:55 am
- 37 Comments
Off-Road Suspension : Getting the perfect Set-Up… As motorcycles get more and more complex, it’s easy to think that the science behind the suspension on your bike is almost too much to understand. Yet knowing how your suspension works and what effect the various adjustments have will help you get the best out of your riding. A bad suspension set up can turn your bike into an uncompromising and unpleasant machine, whereas getting it right can improve your riding dramatically and progress your skills to the next level.
Just a quick ‘cover-all’ here – always check the manual for your bike before making any adjustments OK
THE BASICS
OK so suspension can be broken down into just two essential parts – namely the spring and the damper. Both have very different functions but are relatively useless without each other. The spring holds the weight of the machine and serves to absorb impacts from the ground through riding. However, just absorbing impact alone would not be any use, as the bike would continue to bob up and down like Mr Bobblehead. Consequently, damping is used to slow both the compression of the spring as it squeezes together – unsurprisingly called the compression damping, and how fast it returns to the original dimensions – the rebound damping. Most modern bikes will have adjustment available for the spring and both compression and rebound damping, and it’s getting the balance between these factors right that will make your bike handle well.
At the rear of the machine, most off-road bikes will run an external spring on a single centrally mounted shock absorber, commonly actuated through a linkage system. Damping is inside the structure of the unit, and again commonly there is an external reservoir to the damping system.
At the front, the springs are held internally and up to recently, within both legs. However, the development of SFF systems – Separate Fork Function – for motocross bikes has allowed manufacturers to split the springing and damping function between the two sides, one leg holding the spring, the other handling the damping. For enduro and trail machines, this is less common and most will have both springs and damping systems held internally within each fork leg.
For both front and rear suspension, manufacturers have been developing suspension systems that use air rather than conventional springs, backed up with oil damping. While the rear systems are still very much restricted to the top end race teams, air forks are very much in evidence in the motocross market, although customer response has varied between enthusiastic and sceptical.
Getting your suspension set up is essential to making your bike handle well, but it’s certainly not a simple one hit process. The main factors are how heavy you are and how aggressive a rider you are, but after that there are all manner of other factors to take into account from terrain to weather conditions, and in the case of adventure bikes, how much luggage you are packing.
Most bikes are set up for an average rider who weighs around 12 to 13 stone, so if you are vastly outside this midline, then set-up is going to be harder. Don’t assume that the setting is correct for you even if you are that weight – you still need to check it and adjust accordingly whether your bike is brand new or second-hand.
The best way to get things sorted is to aim to get the bike to a setting that is roughly right for most of the conditions you ride and your style of riding, then look to tweak things slightly to cope with the conditions and terrain on the day.
ALL ABOUT THE SAG
First stop on setting the suspension up for your bike is to set the sag. If you don’t know what this is, sag is the amount the suspension goes down under the weight of the bike alone and under the weight of you sat on the machine. This forms a baseline from which you can adjust everything else.
To start, put your bike onto a paddock stand or centre stand so that both wheels are off the ground. Measure from a point on the swing arm somewhere close to the spindle to a point on the rear mudguard or the top of the number boards. Mark this point you are using with a bit of Gaffer tape so that you come back to the same point.
Then put on all your riding kit including your helmet and boots. Take the bike off the stand and sit on it and bounce up and down a few times to overcome any what’s called ‘stiction’, then get a friend, partner, intelligent child or passer by to measure between the same two points. Subtracting the second measurement from the first will give you the sag – simple. For most dirt bikes, a rule of thumb is around 100mm, but you should check your manual for the recommended figure.
If the sag isn’t at the required level, you are going to need to adjust the preload of the shock spring. Release the pre-load collar lock bolt, and if the sag was more than recommended you will need to tighten the pre-load adjuster – hence compressing the spring – commonly using a bar of drift and a hammer. This approach is really risky if the shock has a plastic especially on older bikes where it may have become brittle, so ideally use a specialist tool from the OEM toolkit instead.
If the sag is less than the recommended level, you will need to slacken off the spring pre-load. In either case, be gentle as you are moving the adjuster and look to do it slowly rather than with jerks on the OEM tool or massive clouts with a drift. Keep sitting on the bike between adjustments to take more measurements until you reach the required sag.
The final stage of the process is now to measure the free sag, which will tell you if the spring in your bike is correct for your weight. With the bike off the centre stand and no rider measure the difference between the previous two points, ideally with someone else holding it upright. Compare this to the static sag, which will tell you how much the machine sags under its own weight. If it’s between 20mm and 30mm then you can be confident that the spring is right for your weight, and you can retighten the pre-load collar.
If however it’s less than this it’s likely that the spring is too soft, as to achieve the required sag has required too much pre-loading of the spring. If it’s more than the 20-300mm ideal, then it’s because the spring is too hard. Both scenarios will mean that you need to get another spring for your shock, but that said if you are 20 stone and the average weight is 12 stone, you might have guessed that! Companies like Hyperpro or K-Tech provide a wide range of springs to cope with both lighter and heavier riders. Fitting a new spring is not difficult if you have both the tools and the knowledge of what is required. If you don’t have both, leave it to a professional.
When it comes to the front of the bike, the process is nothing like as easy or indeed as achievable for the average rider. Most conventional forks don’t have any way to adjust the preload on the springs, so the same level of tuning is not possible. That said, enduro bikes will sometimes have pre-load adjustable via a nut on the top of the fork and the modern breed of air forks have almost infinite adjustments, all of which are possible with nothing more complex than a pump. You do however need to make the adjustments in the correct order, or you risk reducing the travel and totally messing up the suspension! If in real difficulties, you could always read the manual …
As a rule of thumb, your sag and free sag should be roughly the same as the figures you used for the rear, otherwise the bike is going to be unbalanced straight away.
If this is not the case, setting up your forks is best done by a suspension specialist who will be able to identify whether you need pre-load spacers or totally new springs to get the bike to behave correctly. Pay up and look big.
THE DAMPER THE BETTER?
OK so now we’ve sorted the spring, we need to look at the damping. Compression damping, particularly in the case of rear suspension, is commonly split into low speed and high-speed damping. But the terms relate to how fast the shaft of the shock is moving, rather than the actual speed of the bike. Stutter bumps or rocky trails will mean the shock is moving up and down quickly, whereas whooped-out sand tracks will mean the shock is moving more slowly.
Low speed compression damping adjustment is usually by turning the adjuster at the top of the shock absorber reservoir with a flat head screwdriver by the required amount of clicks. High speed compression damping is adjusted using a spanner on the outer nut at the top of the shock reservoir
Either way you want enough compression damping to ensure that you don’t smash though the shock’s movement when you hit bumps, and enough rebound damping that the bike isn’t bouncing like an excited puppy, but not so slow that the shock hasn’t returned for the next bump.
The rebound damping adjuster will be located at the bottom of the shock absorber and can be adjusted with a flat head screwdriver again.
At the front of the bike, the compression and rebound damping adjusters are in different positions, with rebound damping adjusted using a flat head screwdriver or an easy-turn adjuster at the top of the fork unit, and compression damping made in the same way using the adjuster at the bottom of the fork after removing the rubber cap.
With all fork adjustments, make sure you let out any trapped air using the air-bleed screws before any changes are made – you can see it on the image below, along with the rebound adjuster and the pre-load adjuster.
So what happens if you slacken off the rebound? Well, the ride will feel particularly plush and smooth as the wheel will move quickly back, but if you take it too far and the handling will become vague and loose. As you increase the rebound damping, the ride moves from plush and into harsh.
But if less rebound makes the ride nice and plush, why would you want to increase it? The answer is because having too little rebound reduces traction – the wheel pushes back down in a relatively uncontrolled way that can lead to skipping and hence loss of drive.
To make things a little easier here’s a quick guide:
COMPRESSION DAMPING
TOO MUCH
The action of the shock is harsh with far too much resistance to movement and the full suspension travel can’t be used.
TOO LITTLE
The bike feels unstable and uncontrollable with the suspension travelling through the full stoke, breaking traction as it pogos across the ground.
REBOUND DAMPING
TOO MUCH
The bike sits low and returns to the correct height very slowly resulting in poor traction and loss of drive and a harsh ride.
TOO LITTLE
The bike feels nervous and unsettled as the suspension jumps around with every bump.
As you may be gathering now, it’s a delicate balance to get it right and the answer is going to be trial end error if you are going to do it yourself rather than pass this over to a bone-fide suspension specialist. Start at the manufacturer’s OEM settings from your manual and make adjustments in really small increments, marking down what you are changing. Bear in mind that if you do change the springs or increase the preload, then this will feel like the compression takes longer as the suspension will be generally stiffer, so in this case you may need to back off the suspension damping.
Add in the fact that changes to the rear suspension will affect the way the front suspension works and vice versa, then you can see that this is complicated stuff – perhaps why so many riders never touch the stock settings!
FAULT FINDER
So if all the information above has made you feel like you want to tweak your suspension and improve your ride, then here’s our handy fault finder. Work out where your bike is not performing well and the chart will tell you how to solve it.
GENERAL HANDLING
PROBLEM
Suspension feels too hard, ride is harsh and travel not being used.
SOLUTION
Rear – reduce compression damping, reduce spring preload or change spring /spring rate.
Front – reduce compression damping and change springs / spring rate.
PROBLEM
Suspension feels too soft, bike is unstable and bike bottoms out.
SOLUTION
Rear – increase the compression damping, increase spring preload or change spring / spring rate.
Front – Increase compression damping or change springs /spring rate.
CORNERING
PROBLEM
Bike loses traction and breaks away.
SOLUTION
Rear – back off the rebound, reduce spring rate.
Front – back off rebound, raise forks through the clamps to reduce steering angle.
PROBLEM
Rear of bike squats under acceleration.
SOLUTION
Increase rear compression damping. Increase spring pre-load or spring rate.
PROBLEM
Bike dives in corners.
SOLUTION
Increase fork rebound, fork oil level or compression damping.
PROBLEM
Bike turns too swiftly.
SOLUTION
Increase both rebound or compression, drop forks through clamps to increase steering angle.
STRAIGHTS
PROBLEM
Bike bottoms out on larger bumps.
SOLUTION
Rear – Increase compression, increase preload or spring rate.
Front – Increase compression, increase spring rate or oil level.
PROBLEM
Rear of bike kicks around and refuses to stay in line.
SOLUTION
Reduce rear spring rate / change spring, increase rebound damping.
PROBLEM
Handlebar / head shake.
SOLUTION
Increase fork compression damping, change springs / lower spring rate.
PROBLEM
Bike sits low in suspension travel.
SOLUTION
Rear – Increase spring rate, reduce rebound compression.
Front – Increase spring rate, reduce rebound compression.
DROP -OFFS & JUMPS
PROBLEM
Bike bottoms out on landing.
SOLUTION
Rear – increase compression damping, increase spring rate.
Front – Increase compression damping or oil level.
PROBLEM
Suspension rebounds too quickly, bouncing the bike back up.
SOLUTION
Rear – Increase rebound damping.
Front – Increase rebound damping, reduce compression damping, reduce spring rate.
So hopefully this simple guide has given you enough information to head out to the garage and get busy with the tools. Start with the sag and then take the bike to your favourite track or trail and start experimenting – at worst it will make your bike easier to ride, at best it might even make you a better rider. What’s not to like?
Let us know how you get on…
JOIN US FOR THE DIRT BIKE ADVENTURE OF A LIFETIME!
Excellent and helpful post… I am so glad to left comment on this. This has been a so interesting ..I appreciate your effort..
Thanks William – glad we could help
Julian
Great writeup, thanks!
Thanks Corey – glad we could help!
Julian
Excellent write up and break down of how the suspension works. Thanks for also including details how to adjust it based on how the suspension is working. This page is now bookmarked!
Glad we could help Scott
Julian
Shouldn’t you raise the forks in the clamps (fewer lines showing above clamps) to slow down the steering/turn in?
Yes that’s correct
Julian
ST , with the forks sliding them up allowing MORE lines makes for sharper/quicker steering response. Better for tighter riding like enduros. Sliding the forks down allowing LESS lines makes the front of the bike more stable at high speed but slower steering, Hare and Hound type racing.
Thanks for the input Scott
Julian
If the rear wheel hocks up on bigger rocks in low speed (rear wheel dont climb over the rock) what to do?
Hi Mikael
It’s really difficult to diagnose this from just one line – it sounds a bit like your suspension and maybe your tyres are too hard. What bike are you using – if it’s a converted motocrosser then this is commonly a problem if you use them for trail / woods riding
In deep whoop sections after the first 4 or so whoops the rear wheel starts kicking sideways, either direction.
Forks feel fine, Spring weight and sag are correct.
Too much or too little Low speed compression damping??
Hi Greg
It’s hard to diagnose remotely so I would suggest that you have too much compression damping and too little rebound damping. Try backing off the one and increasing the other in small increments until you notice an improvement. Ideally, keep repeating the same track section after each adjustment so you can judge the effects of the changes.
Julian
Fantastic article—after…ahem….40 years of riding off road, I’m going to finally try and get my 500 EXC suspension sorted via this article. It’s always seemed way too daunting–but your help should certainly get me closer. Now, if it’s already in the right ball park, that just means I really AM a crap rider…… Either way, Thank you!
Cheers John – let us know how you get on
Julian
This is exactly the article I was looking for. Something to decode suspension set up. I am looking forward to getting out and giving it my best shot at improving my suspension set up! Thanks.
Thanks Dave
Let us know how you get on!
Julian
HI if oil to much
I am 10cc more than the original oil.
Will it cause incomplete use of the suspension trip?
I riding MT07 Front suspension stroke have 130mm
But i only use up to 65mm it
What mm is the normal condition?
Taiwan is not looking for information in this regard…
Thank.
This is a question for your dealer Lin – sorry we cannot help!
Julian
I have been hunting for knowledge on how to properly set up my KTM 690 Enduro. This is excellent info.
Cheers Byron – glad we could help
Julian
Great info!!!!! I am a novice and got a used 2011 kx450f. Im pretty sure I need softer springs because the free sag was around 53mm. I don’t have any clue what spring weights are on it now. It handles so bad, that I’m not confident at all. I don’t know if anything is wrong with it either. Not enough experience. I can only say that it feels super stiff and I have to fight the bike even at really slow speeds. Almost like I have a front flat. Any suggestion would be really appreciated.
Hi Barry
Thanks for getting in touch. I’d have to say that a KX450 is a tough bike to be a novice on, and if the suspension is really hard, it’s even worse! If I can’t persuade you to downsize to a 250, at least I might be able to get you to take it to a recommended suspension specialist – talk to the guys at your local track to find out who’s good and who’s not. Once you find the right guy, talk through the type of riding you want to do, and how good you are – be honest which is sometimes hard as we are all prone to big-up our own riding! He should be able to get it close and then you might need some additional tweaks once you try out the new set up.
If this is too costly, get yourself a proper manual for the bike, and return everything to stock settings as in the book. This will erase all the fiddling with the settings from previous owners and allow a fresh start, the first step being trying to adjust that sag to the proper level as in our guide. If that can be achieved with the existing spring, then you can progress, but if the previous owner had fitted a harder spring, you need to get it changed, and the same has probably been done with the forks.
If you can – invest the cash in the specialist suspension guy, rather than spending anything else on the bike. It’s the best performance upgrade you will ever make!
Let us know how you get on
Julian
Thanks a lot for the feedback!!!! I have rode dirt bikes before when I was young, But just got back into it after many years. So, I consider myself a novice once again. I am quite sure the springs are too stiff for me because of the sag setting being off as per your instructions. I weigh 167 lbs so stock springs would be the way to go. I fiddled with the clickers and probably made it worse. I can say it feels better when I’m going at some speed, but know something is wrong. If this sounds reasonable, I will find a suspension guy to work with me. What say you? I kind of know this was probably too much bike for me, but am stuck with it. I’ve actually got much better on it until I messed with the clickers. I do know the sag was never right though.
By the way, the Ho chi min trail ride is actually very intriguing to me. I’m definitely considering it!
Then drop Anna an email at anna@rideexpeditions.com – it’s a stunning tour that you will love!
Sort that bike’s suspension!
Julian
This is the simplest, most understandable suspension article I have ever read, except for the “stones” part. 😉 Thank you for clearing the fog! One problem I have is that the front end of my 2007 KTM 300 XC-W smacks really hard when initially landing. I don’t think it is bottoming-out as it is the initial hit I think I feel. If I understand correctly, that should mean it has too much compression dampening. The second problem is the front end slides-out too easily in the corners – even with brand new tires. That would also support backing off the compression dampening, right? Thanks again!
Hi John
Glad the blog helped – we try to cover the subjects that are important! It sounds like your problem is with compression damping so maybe chose a section of a practice track where the problem occurs and adjust it maybe two clicks at a time, ride the section and see what the difference is. Keep going with adjustment and laps until it stops improving and then gets worse the other way and you’ll have found your setting
Julian
Dear Julian,
I just took delivery of a new Yamaha 700 Tenere in the UK and the suspension is very choppy at low bike speeds, really unpleasant.
I found all the settings at least 2-3 clicks harder than the Manual “Standard” settings
Any recommendations where I can get it set-up?
Till then I will try your excellent advice in this lesson, but the T7 only has 1 damping adjustment per end (that is not high and low speed damping) so I am guessing that it is low speed only.
Many thanks
Peter
Derby
Hi Peter
Always start with the settings on standard and change from there. Make sure your preload is set up correctly on the rear, when I tested the bike small adjustments make quite a lot of differences and changes at the back do affect the front and vice versa. Both ends are adjustable for compression and rebound, but as it’s not a full-on enduro or race bike, then there is no high and low speed option. In terms of getting things properly set up, then finding somebody with experience with Adventure bikes is far more difficult than finding an MX guy and as this bike is quite so new, then there won’t be too many that have spend time looking at the Tenere. You could maybe speak to Jim Greenhill who runs Adventure Rider Training – he may even be able to fine tune your riding – search Facebook for A.R.T Adventure Rider Training/Guiding Service and send him a message.
Let us know how you get on – it’s a great bike!
Julian
Great info, just what I needed tahnks
Cheers Steve – glad we could help. Now come on a tour with us!
Julian
Problem with front sitting up and riding over the berm and the rear stepping out in braking approaching a corner and loosing it on corner acceleration is my problem. Also very harsh on landings, mainly the front slapping down hard.
Hi Les
As the article suggests, if you have specific problems then visit a suspension specialist – it will be the best money you ever spend on your bike!
Julian
Brilliant info, best way I’ve seen it explained so far.
Now what about oil weights and air gaps?
😉
Yes Mike you will need both unless you have air forks!
Julian